Thursday, November 24, 2011

Considerations For Your First DIY Guitar Tube Amplifier

!±8± Considerations For Your First DIY Guitar Tube Amplifier

If you have decided to take the plunge and build your own guitar tube amp, please let me share my early projects/mistakes with you to help get you going in the right direction.  But first, be sure you really want to build your own:
You should be fairly handy around electronics already, and aware of the dangers inherent in high voltage tube electronics and the precautions to take when working on tube amps You shouldn't have the expectation that you will save money... unless your time is worth nothing at all you can probably do better purchasing a completed amplifier, even from the kit vendors, but certainly on the open market as used

All said, though, there is a lot of satisfaction in completing and playing an amplifier you built yourself and having the license to further modify/tweak/voice your creation to perfection... so let's get started:

Stumbling Through My first Few Projects

My first project started as an AM radio, it had occured to me that this chassis and most of the components was quite suitable for an octal-tube-based Fender Champ-like single-ended amplifier and I wanted to hear the difference in tone between real tubes and the tube modeling in my Roland Cube amp... After studying some good tube amp books (see resources) I settled upon a plan and:
I fought with the old transformers (insulation turning to dust when you flexed the leads), used tube-sockets, noisy potentiometers and poor physical layout (working with the old radio chassis didn't provide optimum placement of the major components for a tube guitar amplifier) Found out that true point-to-point wiring isn't the best choice for experimenting I couldn't find a non-microphonic old-stock pentode tube The tone sucked... with hindsight I believe it was due to the underwhelming, un-branded, tiny output transformer, but I'll probably never go back to check Bottom-line, I learned a lot but it didn't answer my fundamental questions about tube-tone because I didn't end up with an iconic amplifier as a reference at the end of the project

I spent some frustrating evenings redesigning and reworking my first effort and then for my second major project I broke down and bought a kit that promised a clone of a vintage Champ amplifier.  Major findings included:
Saving a few pennies here and there on components isn't satisfying when you end up investing a lot of time building the project and aspects of the end result look cheap (e.g. a plastic replacement for a 'proper' metal construction jeweled pilot light) or worse... sacrifice tone (e.g. cheap electrolytic capacitors) I've grown a bit leary of un-branded chinese transformers that may not have even been hi-pot tested let alone certified by a safety agency; and who knows what laminations, etc. are used in the audio transformer? Tiny chassis and cabinets aren't the best choice for adding additional functionality to the stock circuit and very frustrating to work with 8″ speakers and small cabinets suck tone... this amplifier sounds great when you plug it into a proper speaker & cabinet combination
Your First DIY Guitar Tube Amp Project

With the above experiences in mind it is time to summarize some considerations for the first project:
Simple project but not under-featured... something that will be satisfying and playable Physically large for easy access, simplified assembly and room to modify Well documented, well supported... not necessarily with user's manuals and step-by-step construction guides, but rather by a community with active forums, or extensive web documentation, etc. A complete kit of parts, no difficult sourcing of components Good quality parts with the potential to upgrade them if desired... but moderation rules... you may want good value over extravagant components to minimize your downside if your project doesn't come out well or you lose interest. Standard sized chassis for easy sourcing of cabinets, or cabinets available from the kit supplier, or a desire, determination and ability to build (and finish) your own cabinetry

With the above given due consideration my third time was the charm! 

I recommend you search out a reputable supplier of tube-amp kits, and pick a model that suits both your taste in tone and a satisfying set of features for your first DIY Guitar Tube Amp!


Considerations For Your First DIY Guitar Tube Amplifier

Geneva State Park Lodge Save

Monday, November 14, 2011

The Ultimate Tone - A Book Review of the Best DIY Guitar Tube Amplifier Series

!±8± The Ultimate Tone - A Book Review of the Best DIY Guitar Tube Amplifier Series

This article is a book review on a series of six books that is the most comprehensive and lucid explanation of guitar tube amp architecture, circuits, tone, components and construction technique for DIYers I have ever found. The review deals with each book separately and recommends purchasing them in a specific order to grow your knowledge in step with your building experience.

Kevin O'Connor of London Power has created a series of books under the main title of "The Ultimate Tone." These books are truly unique and carefully tailored for the Do-It-Yourself (DIY) guitar tube amp hobbyist and boutique amplifier builder. The books have a home-made 'feel' as well... all the illustrations are done by hand and the books are photocopy-printed on 8.5″x11″ paper and bound with plastic spines and clear plastic covers. There are six books in the series now with the most recent being released in the late spring of 2008. You may want to buy the entire series all at once and get a modest savings, but I think you should consider buying them one at a time and digest as you go, building projects along the way. A key point though... you don't necessarily want to buy them in numerical order. I recommend the following sequence:

The Ultimate Tone Volume 3 - Generations of Tone The Ultimate Tone Volume 5 - Tone Capture The Ultimate Tone Volume 2 - Systems Approach to Stage Sound Nirvana The Ultimate Tone Volume 4 - Advanced Techniques for Modern Guitar Amp Design The Ultimate Tone - Modifying and Custom Building Tube Guitar Amps The Ultimate Tone Volume 6 - Timeless Tone Built for the Future Today
The Ultimate Tone Volume 3 - Generations of Tone

This is the most important book in the series for the beginning tube amp builder.

Chapters 2 through 4 lay down the foundation of good DIY tube amp construction, filling you in on good electrical connections, grounding technique, lead dress and other wiring techniques, and mechanical layout including assembly methods like terminal strips, turret and eyelet boards.

The subsequent chapters each pick a particular 'iconic' amplifier, each iconic amplifier being a prototypical example of amplifiers of its class, and they are examined in detail as to the circuit topology, peculiar tonal characteristics that result and fatal flaws that the product is notorious for. Kevin provides the original schematics and then shows how you can apply the techniques detailed in the earlier chapters to improve the performance and reliability of the icon without harming the tone. The schematics are redrawn, layouts are provided and mechanical solutions are worked out to make each chapter a complete, self-contained, build-it-yourself amp project.

This process is repeated for several variations of the Champ in chapter 5 (this chapter greatly influenced my own single-ended amp project), then in quick succession: the Bassman, Plexi, 800, Bull Dog, AC-30, Portaflex, SVT, Bass Master, Custom Special, Guitar Mate, Herzog and Laney amplifiers are dealt with.

If you can only buy one book for your DIY guitar amp hobby I'd heartily recommend this one.

The Ultimate Tone Volume 5 - Tone Capture

Volume 5 picks up where Volume 3 left off, with a project-oriented approach and some sophisticated DIY tube amp solutions for guitar and bass.

The book starts off with a chapter overviewing vacuum tube operation called 'tube tone,' followed up by a chapter on guitar electronics and pickup characteristics.

The next two chapters are small projects: Sigma for effects switching and Triple-X for amplifier switching.

Chapters 5 & 6 are on transformers... important components but it made me yawn, sorry.

Starting with chapter 7, all the stops are pulled out and you are in project heaven... Major (200W), Soma 84 (EL84 amp), Standard (the London Power Standard Preamp from 1995 coupled to a 50W amp using four power tubes), Doppelsonde (mixing power tube types), AX84 (discussion on the original goal of a very low output power amp), Kelly (50W from 4 6V6s), and several other projects of lesser scope.

One favorite project I did was based on Kevin's reworking of the HotBox tube preamp pedal from Matchless in chapter 16. I built this pedal in a truly "true point-to-point style" (meaning terminal strips) in a tube pedal enclosure from Doug Hoffman, substituting a Baxandall tone stack and reworking the preamp values to be more Dumble-esqe (non-HRM type).

What would you do to match an amplifier to Yngwie Malmsteen's style? See chapter 18, 'Swede.'

The Ultimate Tone Volume 2 - Systems Approach to Stage Sound Nirvana

Volume 2 is not project oriented. The bulk of the book, chapters 2 through 5, deals with power supply tricks and a comprehensive overview of power amplifiers, including tube, solid-state and hybrid power amps. Chapter 3, on tube power amplifiers, has some very practical information on mods and fixes to Marshall and Fender bias circuits.

I like the 1st and last chapters of Volume 2 the best. The first chapter is a short discussion of sound stages and how you might setup your gear on stage for the best audience/band experience. The last, chapter 6, is called "Pillars of Tone" and in this chapter the major contributors tone at the block-level of a guitar tube amplifier system design are discussed one by one and Kevin provides some very valuable insight into tone shaping throughout the preamp/amplifier.

The Ultimate Tone Volume 4 - Advanced Techniques for Modern Guitar Amp Design

This is the book you'll want to buy if you feel the need to get deeply involved with the power scaling technology that Kevin has developed. Power Scaling, coined and trademarked by Kevin, is the way you can get aspects of power amp distortion (as opposed to preamp distortion) into your tone at bedroom volume levels. Volume 4 is not DIY project oriented but explores the issues, including attenuation, power scaling (both down and up), sag, and power management, tackled by modern guitar tube amp designers.

That said, the second-to-last chapter in Volume 4 might be important for a broader group of enthusiast builders... design philosophy. In this chapter Kevin provides a hierarchical design process that could be used to make key decisions on how you approach your next project.

The Ultimate Tone - Modifying and Custom Building Tube Guitar Amps

There is no volume number in the title of this book, it was the 1st. Personally, I bought it for completeness. I specifically wanted to have the 'perfect effects loop' information, although the loop itself is incorporated into a project in Volume 5. TUT also has some excellent material on reverbs and signal switching methods that is not explained in the other volumes. The first half of TUT introduces/overviews tube amp systems, power supplies & grounds then focuses on preamp and power amp modifications to commercial amplifiers (e.g. Marshall / Fender)... if you are totally new to tube electronics you may want to buy this 1st volume at the same time as Volume 3.

The Ultimate Tone Volume 6 - Timeless Tone Built for the Future Today

In many ways, Volume 6 is a continuation and extension of the material in Volume 4, where Power Scaling is introduced.  In Volume 6 a new 'direct control' version of Powerscaling is featured which was introduced in Vol 4 but flushed out with comprehensive circuits and applied to 'sag' and sustain control as well in Vol 6.  The new scaling circuits have many advantages for a DIY builder like greater noise immunity and less sensitivity to layout, etc.

I applied the new DC Power Scaling to a Trainwreck clone project and was really impressed with the improvement in 'playability' at lower volumes... the unmodified Trainwreck Express circuit is just too loud for domestic use, needing to be cranked to get the sweet tones it is renowned for.

One of the chapters in Volume 6 is dedicated to the Dumble amplifiers... something I was really looking forward to since many of my hobby projects focus on those circuits.  I found this short chapter to be a good introduction to the overall architecture of the Dumble amps, written from the point of view of the evolution from the early modified standard amps that Alexander Dumble started out doing, but I felt the chapter fell short in discussing some of the more important subtleties of the later Dumble models.

Volume 6 also has lots of other material in it, including a great tutorial on designing really high output power amplifiers and a great chapter on high gain amplifier designs with real-world circuits referenced and detailed.

In Summary...

Kevin's books have a very empirical approach. He encourages you to set aside convention in some instances or not be afraid to try combinations of tubes or even pulling tubes and in all cases clearly explains why it is o.k. and points out any reasons why it wouldn't be o.k. All the examples in the books are very practical and he certainly has the DIYer in mind as he is writing.

Kevin's body of work is truly encyclopedic in nature, and considering that, one feature sorely lacking from his books is any kind of indexing... this is aggravated by the fact that Kevin constantly refers to previous writings rather than repeat himself in a new volume, and it is very difficult to put your finger on the reference even with the other book in hand. Perhaps search engine technology, like Google's ability to search protected content, could be put to good use in this case and provide a kind of 'auto-index' on the web of all of Kevin's books without actually giving away the book itself. Or better yet, how about an e-book format of Kevin's entire collection of TUT books... I think all of the e-book readers include searching capabilities... and Kevin's hand-drawn schematics would probably scale adequately and be very readable on the e-paper displays these devices feature.

Meanwhile, how do you get Kevin's books today? The best way to get the books is to directly order them from London Power Press. They now have a shopping cart on http://www.londonpower.com.


The Ultimate Tone - A Book Review of the Best DIY Guitar Tube Amplifier Series

Swiffer Floor Cleaner For Sale


Twitter Facebook Flickr RSS



Français Deutsch Italiano Português
Español 日本語 한국의 中国简体。







Sponsor Links